Armrest

ABSTRACT

An armrest attachable to a seat back includes: an arm frame; and a clutch through which the arm frame is rotatably supported by the seat back. The clutch includes: an inner member (inner race) configured to be fixed to one of the arm frame and the seat back; an outer race provided radially outward of the inner member and spaced apart from the inner member, and configured to be fixed to the other one of the arm frame and the seat back; an unlocking member provided coaxially with the inner member and the outer race and configured to be rotatable relative to both of the inner member and the outer race; and an unlocking manipulation mechanism configured to actuate the unlocking member to unlock a locked state.

TECHNICAL FIELD

The present invention relates to an armrest, in particular to an armrest using a clutch which can be downsized in an axial direction.

BACKGROUND ART

In some passenger cars, a seat may be provided with an armrest. As disclosed in Patent Literature 1, a certain improved armrest is configured such that the rotation of the armrest in a downward direction is locked within an angle range of the armrest in a use state, but the armrest is allowed to rotate freely in upward and downward directions within the other angle range of the armrest in a non-use state.

The armrest disclosed in Patent Literature 1 employs as a one-way clutch mechanism for locking the rotation of the armrest in the downward direction a structure including a shaft and a coil spring wound around the outer periphery of the shaft. This configuration utilizes the characteristic of the coil spring such that when the rotation is made in the same direction as that in which the coil spring is wound up, the rotation of the coil spring with respect to the shaft is locked, but the rotation made in the reverse direction in which the coil spring is unlocked is allowed.

CITATION LIST Patent Literatures

Patent Literature 1: Japanese Laid-open Patent Application, Publication No. 2009-261828

SUMMARY OF INVENTION Technical Problem

However, a one-way clutch mechanism using a coil spring as disclosed in Patent Literature 1 has a problem that the size of the coil spring in its axial direction is large. In a roller-type one-way clutch mechanism including rollers disposed between an inner race and an outer race, the size of the one-way clutch mechanism can be made relatively smaller in the axial direction; however, there is no known structure for unlocking the one-way clutch function in a predetermined angle range only by rotating the inner race or the outer race with a predetermined rotating action.

In view of the above-background, the present invention seeks to provide an armrest using a clutch which can be downsized in the axial direction.

Further, the present invention also seeks to provide an armrest which can be reduced in weight. Further, the present invention seeks to provide an armrest in which a locally weakened portion would be unlikely to be produced even if the weight is reduced.

Further, the present invention also seeks to provide an armrest in which the inner race or the outer race can be prevented from receiving an excessive radial load.

Further, the present invention also seeks to provide an armrest of which the unlocking operation can be performed easily so that improvement in the easy operability can be achieved.

Further, the present invention seeks to provide a one-way clutch, as a clutch used for an armrest, which one-way clutch can be downsized in the axial direction and can allow the inner race and the outer race to be disengaged by a predetermined operation, thereby making the inner race and the outer race rotatable relative to each other.

Further, the present invention also seeks to provide a one-way clutch in which the inner race and the outer race can be prevented from receiving an excessive radial load.

Further, the present invention also seeks to provide a one-way of which the unlocking operation can be performed easily so that improvement in the easy operability can be achieved.

Further, another object of the present invention is to reduce the weight of each of the constituting elements for the one-way clutch as well as to improve the rigidity of these constituting elements. Further, the present invention seeks to provide a one-way clutch which can allow each of the constituting elements for the one-way clutch to be manufactured easily as well as to reduce the number of the constituent parts.

Solution to Problem

In order to solve the above-described problem, an armrest according to the present invention is an armrest attachable to a seat back, comprising: an arm frame; and a clutch through which the arm frame is rotatably supported by the seat back, wherein the clutch comprises: an inner member configured to be fixed to one of the arm frame and the seat back; an outer race provided radially outward of the inner member and spaced apart from the inner member, and configured to be fixed to the other one of the arm frame and the seat back; an unlocking member provided coaxially with the inner member and the outer race, and configured to be rotatable relative to both of the inner member and the outer race; and an unlocking manipulation mechanism configured to actuate the unlocking member to unlock a locked state.

With this configuration of the armrest, since a shaft and a coil spring are not used, the size in the axial direction can be reduced.

In the above-described armrest, the inner member may be an inner race; and the armrest may comprise a movable piece received in a pocket which is located between the inner race and the outer race and includes a portion whose radial width decreases with distance toward one circumferential direction; the unlocking member may have an unlocking piece arranged adjacent to one side of the movable piece in the one circumferential direction; and the unlocking manipulation mechanism may be configured to actuate the unlocking member to unlock the locked state in which the movable piece is trapped by inner walls of the pocket.

With this configuration of the armrest, the movable piece received in the pocket enables locking without using a shaft and a coil spring, and the unlocking member and the unlocking manipulation mechanism can unlock the locked state. Accordingly, the size in the axial direction can be reduced.

In the above-described armrest, the clutch may be a one-way clutch; and the unlocking manipulation mechanism may include a first manipulation member configured to be engaged with or fixed to the unlocking member, and a switching member configured to be coaxial with and rotatable relative to both of the inner race and the outer race and having a circumferential surface; the first manipulation member may contact the circumferential surface of the switching member, and the circumferential surface of the switching member may include a small diameter portion and a large diameter portion having a diameter greater than that of the small diameter portion; one of the inner race and the outer race may have a rotation restricting portion engageable with the switching member to restrict a relative rotation thereof with respect to the switching member in a predetermined angular range; the circumferential surface may be provided with a return engagement portion protruding radially from the circumferential surface, and when the first manipulation member is brought into contact with one of the small diameter portion and the large diameter portion, the unlocking member is allowed to rotate in the one circumferential direction to cause the movable piece to be trapped and thus locked by the inner walls of the pocket, whereas when the first manipulation member is brought into contact with the other one of the small diameter portion and the large diameter portion, the unlocking member is allowed to rotate in the other circumferential direction to unlock the locked state of the movable piece.

With this configuration, when one of the inner race and the outer race is rotated with respect to the other one of them, the switching member relatively rotates with respect to the first manipulation member in conjunction with the rotation of the one of the inner race and the outer race. For this reason, if one of the inner race and the outer race is rotated, a contacting point of the first manipulation member which contacts the circumferential surface of the switching member is switched between the large diameter portion and the small diameter portion in accordance with the phase (direction) of the switching member. Since the first manipulation member is engaged with or fixed to the unlocking member, the unlocking member slightly rotates in a circumferential direction. This can cause the unlocking piece of the unlocking member to rotate in one circumferential direction or in the other circumferential direction. In the case of rotation in the one circumferential direction (i.e., direction in which the radial width of the pocket decreases), the movable piece is trapped and thus locked in the pocket. Namely, the inner race and the outer race are engaged with each other so that they are not rotatable relative to each other. On the other hand, when the unlocking member is rotated in the other circumferential direction, the unlocking piece pushes the movable piece toward the direction in which the radial width of the pocket becomes larger to unlock the locked state. In other words, the inner race and the outer race become freely rotatable relative to each other.

As described above, according to the present invention, the armrest including the movable piece in the pocket can perform locking and locking operations by rotating the armrest.

Further, the inner race having the rotation restricting portion or the outer race having the rotation restricting portion can be freely rotatable relative to the switching member in the range where the rotation restricting portion does not restrict the relative rotation with respect to the switching member. On the other hand, in the range where the rotation is restricted, the inner race having the rotation restricting portion or the outer race having the rotation restricting portion rotates together with the switching member. When the switching member and one of the inner race and the outer race rotate together, the switching member and the first manipulation member rotate relatively to each other, so that the contacting point of the first manipulation member which contacts the circumferential surface of the switching member is switched between the small diameter portion and the large diameter portion. In this configuration, since the circumferential surface is provided with the return engagement portion protruding radially outward from the circumferential surface, for example, the first manipulation member, which is in contact with the large diameter portion after rotating one of the inner race and the outer race to ride over the return engagement portion, can engage with the return engagement portion by the reverse rotation of one of the inner race and the outer race and cause the switching member to rotate in the reverse direction. Namely, since not only is the switching member rotatable relative to the inner race or the outer race in one direction but also rotatable in the reverse direction, one of the inner race and the outer race can be moved back and forth relative to the other one of them. In the back and forth motions, the locked state and the unlocked state of the inner race and the outer race can be switched over in accordance with whether the first manipulation member contacts with the large diameter portion or the small diameter portion, both of which are provided on the circumferential surface of the switching member.

The expression “the switching member relatively rotates with respect to the first manipulation member” includes the case where, as viewed from outside, the first manipulation member is rotatable while the switching member is stationary. This is because, in this example too, the switching member rotates relatively with respect to the first manipulation member.

In the above-described armrest, the inner race may comprise a first metal part constituting a part of the inner walls of the pocket, and a first resin part; and a rugged portion formed on an inner periphery of the first metal part and a rugged portion formed on an outer periphery of the first resin part may be engaged with each other such that the first metal part and the first resin part are assembled together to prevent relative slippage in circumferential directions.

With this configuration, weight reduction can be achieved by using the first resin part while the strength required for the inner race is provided by the first metal part.

Further, the above-described armrest may further comprise an urging member arranged to urge the movable piece toward the one circumferential direction, and the inner race may comprise a first metal part constituting a part of the inner walls of the pocket, and a first resin part; a rugged portion formed on an inner periphery of the first metal part and a rugged portion formed on an outer periphery of the first resin part may be engaged with each other such that the first metal part and the first resin part are assembled together to prevent relative slippage in circumferential directions; at the outer periphery of the first metal part, the first metal part may have an urging member receiving recess which is recessed toward a center of the first metal part to receive the urging member; and the rugged portion of the first metal part may have a protrusive portion protruding toward the center of the first metal part, and the protrusive portion may be arranged radially inward of the urging member receiving recess.

With this configuration, weight reduction can be achieved by using the first resin part while the strength required for the inner race is provided by the first metal part, and further the radial width of the first metal part is increased to avoid the presence of a locally weakened portion that would occur at the first metal part.

In the above-described armrest, the outer race may comprise a second metal part constituting a part of the inner walls of the pocket, and a second resin part, and a rugged portion formed on an outer periphery of the second metal part and a rugged portion formed on an inner periphery of the second resin part may be engaged with each other such that the second metal part and the second resin part are assembled together to prevent relative slippage in circumferential directions.

With this configuration, weight reduction can be achieved by using the second metal part while the strength required for the outer race is provided by the second metal part.

In the above-described armrest, it is preferable that the rugged portion of the second metal part has a protrusive portion protruding radially outward, and when the clutch is in the locked state, the protrusive portion is positioned radially outward of the movable piece.

According to this configuration, the contact pressure of the movable piece can be received by a high rigidity portion of the second metal part, which can ensure the strength of the second metal part.

In the above-described armrest, it is preferable that the unlocking member has an extension portion extending radially outward, and that the first manipulation member engages with the unlocking member at the extension portion, and the first manipulation member is arranged radially outward of the outer race in a region where the first manipulation member and the outer race overlap in an axial direction.

With this configuration, since the first manipulation member is arranged radially outward of the outer race in a region where the first manipulation member and the outer race overlap in the axial direction, the size in the axial direction is less likely to increase even if the first manipulation member is provided. In other words, the size in the axial direction can be reduced.

In the above-described armrest, it is preferable that the inner walls of the pocket have a projection at one side of the movable piece in the one circumferential direction, and when the inner race and the outer race are forcibly and relatively rotated in a locking direction, the projection contacts the movable piece.

With this configuration, when the inner race and the outer race are forcibly rotated in the locking direction, the projection and the movable piece are brought into contact so that the movable piece is not strongly trapped by the er wall the inner walls the pocket any more. This can prevent the inner race or the outer race from receiving an excessive radial load.

In the above-described armrest, the unlocking manipulation mechanism may be engaged with or fixed to the unlocking member and include a second manipulation member extending toward a distal end of the arm frame, and when the second manipulation member is manipulated to rotate the unlocking member in the other circumferential direction, the movable piece may be allowed to be unlocked.

With this configuration, not only can locking and unlocking be performed by the predetermined relative rotation of the inner race and the outer race but also the unlocking can be performed by the manipulation of the second manipulation member. This can improve the easy operability.

In the above-described armrest, it is preferable that: the unlocking manipulation mechanism is engaged with or fixed to the unlocking member and includes a second manipulation member extending toward a distal end of the arm frame; that when the second manipulation member is manipulated to rotate the unlocking member in the other circumferential direction, the movable piece is allowed to be unlocked: that the first manipulation member is provided arcuately around an axis of rotation of the arm frame, and the second manipulation member is provided along a longitudinal direction of the arm flame; and that the first manipulation member and the second manipulation member are arranged so as not to overlap each other as viewed from an axial direction.

According to this configuration, since the first manipulation member and the second manipulation member are arranged so as not to overlap each other as viewed from the axis of rotation of the arm rest, the size in the axial direction is less likely to increase even if the first manipulation member and the second manipulation member are provided.

In the above-described armrest, it is preferable that the small diameter portion and the large diameter portion are formed as flanges extending from a peripheral edge of the switching member in an axial direction of the switching member.

With this configuration, while the weight of the switching member can be reduced, it is possible to enlarge the sliding contact surface contacting with the contacting portion.

In this armrest, it is preferable that the flange constituting the small diameter portion and the flange constituting the large diameter portion are connected to each other. This can improve the rigidity of the switching member.

Further, in the above-described armrest, it is preferable that the return engagement portion is integrally molded with the switching member. This can ease the manufacture of the return engagement portion, and the number of the constituent parts can be reduced.

Further, in the above-described armrest, it is preferable that the extension portion is integrally molded with the unlocking member. This can ease the manufacture of the extension portion, and the number of the constituent parts can be reduced.

In the above-described armrest, it is preferable that: a first attachment member is fixed to the inner race and a second attachment member is fixed to the outer race; that one of the first attachment member and the second attachment member has a stopper which protrudes toward the one-way clutch and is engageable with the inner race or the outer race fixed to the other one of the first attachment member and the second attachment member to restrict a rotation range of the one of the first attachment member and the second attachment member; and that the stopper is arranged in a region where the stopper and the extension portion overlap in the axial direction and where the stopper and the extension portion do not overlap as viewed from the axial direction.

According to this configuration, since the extension portion and the stopper are arranged in a region where they do not overlap each other as viewed from the axial direction and where they overlap in the axial direction, the size of the armrest can be further reduced in the axial direction.

Further, a clutch used for the above-described armrest comprises: an inner race; an outer race provided radially outward of the inner race and spaced apart from the inner race; a movable piece received in a pocket which is located between the inner race and the outer race and includes a portion whose radial width decreases with distance toward one circumferential direction; an unlocking member provided coaxial with the inner race and the outer race and configured to be rotatable relative to both of the inner race and the outer race: a first manipulation member configured to be engaged with or fixed to the unlocking member; and a switching member configured to be relatively rotatable with respect to the first manipulation member in conjunction with rotation of one of the inner race and the outer race and having a circumferential surface, wherein the unlocking member has an unlocking piece arranged adjacent to one side of the movable piece in the one circumferential direction, wherein the first manipulation member contacts the circumferential surface of the switching member, and the circumferential surface of the switching member includes a small diameter portion and a large diameter portion having a diameter greater than that of the small diameter portion, and wherein when the first manipulation member is brought into contact with one of the small diameter portion and the large diameter portion, the unlocking member is allowed to rotate in the one circumferential direction to cause the movable piece to be trapped and thus locked in the pocket, whereas when the first manipulation member is brought into contact with the other one of the small diameter portion and the large diameter portion, the unlocking member is allowed to rotate in the other circumferential direction to unlock the locked state of the movable piece.

With this configuration, when one of the inner race and the outer race is rotated with respect to the other one of them, the switching member relatively rotates with respect to the first manipulation member in conjunction with the rotation of the one of the inner race and the outer race. For this reason, if one of the inner race and the outer race is rotated, a contacting point of the first manipulation member which contacts the circumferential surface of the switching member is switched between the large diameter portion and the small diameter portion in accordance with the phase (direction) of the switching member. Since the first manipulation member is engaged with or fixed to the unlocking member, the unlocking member slightly rotates in a circumferential direction. This can cause the unlocking piece of the unlocking member to rotate in one circumferential direction or in the other circumferential direction. In the case of rotation in the one circumferential direction (i.e., direction in which the radial width of the pocket decreases), the movable piece is trapped and thus locked in the pocket. Namely, the inner race and the outer race are engaged with each other so that they are not rotatable relative to each other. On the other hand, when the unlocking member is rotated in the other circumferential direction, the unlocking piece pushes the movable piece toward the direction in which the radial width of the pocket becomes larger to unlock the locked state. In other words, the inner race and the outer race become freely rotatable relative to each other.

As described above, according to the present invention, the one-way clutch including the movable piece provided in the pocket can perform locking and locking operations by rotating one of the inner race and the outer race. Namely, the size of the one-way clutch can be reduced in the axial direction, and the one-way clutch can allow the engagement between the inner race and the outer race to be disengaged by a predetermined operation, thereby slipping the inner race and the outer race relative to each other.

The expression “the switching member relatively rotates with respect to the first manipulation member” includes the case where, as viewed from outside, the first manipulation member is rotatable while the switching member is stationary. This is because, in this example too, the switching member rotates relatively with respect to the first manipulation member.

In the above-described one-way clutch, the switching member may be configured to be rotatable relative to both of the inner race and the outer race, and one of the inner race and the outer race may have a rotation restricting portion engageable with the switching member to restrict a relative rotation thereof with respect to the switching member in a predetermined angular range, and further the circumferential surface may be provided with a return engagement portion protruding radially outward from the circumferential surface.

With this configuration, the inner race having the rotation restricting portion or the outer race having the rotation restricting portion can be freely rotatable relative to the switching member in the range where the rotation restricting portion does not restrict the relative rotation with respect to the switching member. On the other hand, in the range where the rotation is restricted the inner race having the rotation restricting portion or the outer race having the rotation restricting portion can rotate together with the switching member. When the switching member and one of the inner race and the outer race rotate together, the switching member and the first manipulation member rotate relatively to each other, so that the contacting point of the first manipulation member which contacts the circumferential surface of the switching member is switched between the large diameter portion and the large diameter portion. In this configuration, since the circumferential surface is provided with the return engagement portion protruding radially outward from the circumferential surface, for example, the first manipulation member, which is in contact with the large diameter portion after rotating one of the inner race and the outer race to ride over the return engagement portion, can engage with the return engagement portion by the reverse rotation of one of the inner race and the outer race and cause the switching member to rotate in the reverse direction. Namely, since not only is the switching member rotatable relative to the inner race or the outer race in one direction but also rotatable in the reverse direction, one of the inner race and the outer race can be moved back and forth relative to the other one of them. In the back and forth motions, the locked state and the unlocked state of the inner race and the outer race can be switched in accordance with whether the first manipulation member contacts with the large diameter portion or the small diameter portion, both of which are provided on the circumferential surface of the switching member.

In the above-described one-way clutch, it is preferable that the unlocking member has an extension portion extending radially outward, and that the first manipulation member engages with the unlocking member at the extension portion, and the first manipulation member is arranged radially outward of the outer race in a region where the first manipulation member and the outer race overlap in an axial direction.

With this configuration, since the first manipulation member is arranged radially outward of the outer race in a region where the first manipulation member and the outer race overlap in the axial direction, the size in the axial direction is less likely to increase even if the first manipulation member is provided. In other words, the size in the axial direction can be reduced.

In the above-described one-way clutch, it is preferable that the inner walls of the pocket have a projection at one side of the movable piece in the one circumferential direction, and when the inner race and the outer race are forcibly and relatively rotated in a locking direction, the projection contacts the movable piece.

With this configuration, when the inner race and the outer race are forcibly rotated in the locking direction, the projection and the movable piece are brought into contact so that the movable piece is not strongly trapped by the inner walls of the pocket any more. This can prevent the inner race or the outer race from receiving an excessive radial load.

The above-described one-way clutch may further comprise a second manipulation member engaged with or fixed to the unlocking member, and it is preferable that when the second manipulation member is manipulated to rotate the unlocking member in the other circumferential direction, the inner race and the outer race are allowed to be unlocked.

With this configuration, not only can locking and unlocking be performed by the predetermined relative rotation of the inner race and the outer race but also the unlocking can be performed by the manipulation of the second manipulation member. This can improve the easy operability.

In the above-described one-way clutch, it is preferable that the small diameter portion and the large diameter portion are formed as flanges extending from a peripheral edge of the switching member in an axial direction of the switching member.

With this configuration while the weight of the switching member can be reduced, it is possible to enlarge the sliding contact surface contacting with the contacting portion.

In this one-way clutch, it is preferable that the flange constituting the small diameter portion and the flange constituting the large diameter portion are connected to each other. This can improve the rigidity of the switching member.

Further, in the above-described one-way clutch, it is preferable that the return engagement portion is integrally molded with the switching member. This can ease the manufacture of the return engagement portion, and the number of the constituent parts can be reduced.

Further, in the above-described one-way clutch, it is preferable that the extension portion is integrally molded with the unlocking member. This can ease the manufacture of the extension portion, and the number of the constituent parts can be reduced.

In the above-described one-way clutch, it is preferable that: a first attachment member is fixed to the inner race and a second attachment member is fixed to the outer race: that one of the first attachment member and the second attachment member has a stopper which protrudes toward the one-way clutch and is engageable with the inner race or the outer race fixed to the other one of the first attachment member and the second attachment member to restrict a rotation range of the one of the first attachment member and the second attachment member; and that the stopper is arranged in a region where the stopper and the extension portion overlap in the axial direction and where the stopper and the extension portion do not overlap as viewed from the axial direction.

According to this configuration, since the extension portion and the stopper are arranged in a region where they do not overlap each other as viewed from the axial direction and where they overlap in the axial direction, the size of the one-way clutch can be further reduced in the axial direction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a seat with an armrest.

FIG. 2 shows left-side views explaining the motion of the armrest, in which (a) shows a stowing operation, and (b) shows a folding out operation.

FIG. 3 is an exploded perspective view of the armrest.

FIG. 4 includes (a) a right-side view of an outer race, and (b) a cross-sectional view taken along the line IV-IV of (a).

FIG. 5 is a view showing the inner structure of a one-way clutch.

FIG. 6 shows views explaining the motion of a roller, in which (a) shows rotation in an unlocking direction, (b) shows rotation in a locking direction, and (c) shows the roller in an unlocked state.

FIG. 7 includes view of the one-way clutch observed when the armrest is in a fold out position (position A), in which (a) shows a left-side view of the one-way clutch, and (b) shows a view of the one-way clutch as seen from below.

FIG. 8 is a left-side view of the one-way clutch in a locked state when the armrest is located near the position B.

FIG. 9 is a left-side view of the one-way clutch in an unlocked state when the armrest is located near the position B.

FIG. 10 is a left-side view of the one-way clutch in an unlocked state when the armrest is in a stowed position (position C).

FIG. 11 is a left-side view of the one-way clutch in the unlocked state when the armrest is rotated from the stowed position toward the fold out position and is located near the position A.

FIG. 12 is an enlarged view showing the structure around the roller of the one-way clutch according to a modified embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a description will be given of one embodiment of an armrest as a movable member according to the present invention. As seen in FIG. 1, a seat S includes a seat back S1 and a seat bottom S2, and an armrest (first attachment member) R is fixed to the seat back (second attachment member) S1 through a one-way clutch 1 which is an example of a clutch. The following description will be given of the case in which, the armrest R provided at the right side of the seat back S1 as shown in FIG. 1 is seen from the left side. In this specification, directions of front, rear, right, left, upper and lower are designated as from the view point of an occupant sitting on the seat S, and for example, a view of the armrest R as seen from left (e.g., FIG. 2) is referred to as a left-side view of the armrest R for convenience.

As seen in FIGS. 2 (a) and (b), the armrest R is rotatable between a fold out state (position A) in which the distal end of the armrest faces frontward and a stowed state (position C) in which the distal end of the armrest faces upward. As seen in FIG. 2 (a), during the stowing operation for moving the armrest in a predetermined angle range from the fold out state toward the stowed state (in a range from the position A to the position B), the armrest R is allowed to rotate upward but is not allowed to rotate downward. The state in which the armrest is not allowed to rotate downward is referred to as being “locked” (locked state) in this specification. In contrast, during the stowing operation, the armrest R is allowed to rotate both upward and downward in a range from the position B to the position C. This state is referred to as being unlocked (unlocked state). Further, as seen in FIG. 2 (b), the armrest R is allowed to rotate both upward and downward during the folding out operation for moving the armrest R from the stowed position (position C) toward the fold out position (position A). In other words, the armrest R is in the unlocked state.

In the folding out operation, when the armrest R is completely rotated to the position A, it returns to the locked state. However, independent of the above operation, the armrest R can be unlocked in any posture by depressing a lower portion of a manipulation lever R2 provided at the distal end of the armrest R.

The configuration for performing the above-described function of the armrest R will be described below.

As seen in FIG. 3, the armrest R includes an arm frame R1 made of plastic resin; although not shown in the drawings, a cushion and a skin are provided outside the arm frame R1. The arm frame R1 has a shape extending in the front-rear direction of FIG. 3, and the rear end portion of the arm frame R1 is rotatably attached to the seat back S1 through the one-way clutch 1 using a bolt (not shown) or the like. At the rear end portion of the arm frame R1, an inner race 2B made of plastic resin, which is an example of a first resinous member, is formed on the left side. Provided on the outer periphery of the plastic inner race 2B is a rugged shaped portion (rugged portion) 21B having different outer diameters arranged at a constant pitch.

Provided radially outward of the plastic inner race 2B are stoppers R4 protruding leftward (toward the one-way clutch 1) at two opposite positions across the plastic inner race 2B. The stoppers R4 are engageable with stoppers 38 of an outer race 3 (one of the inner race 2 and the outer race 3 fixed to the seat back S1) to be described later in a circumferential direction, to thereby restrict a relative rotation range of the outer race 3 and the arm frame R1.

The one-way clutch 1 includes the inner race 2, the outer race 3, rollers 71 as an example movable pieces, and springs 72 as an example of urging members. The one-way clutch 1 further includes, as an unlocking manipulation mechanism for unlocking a locked state in which each roller 71 is trapped by the inner walls of a pocket PK, an unlocking member 4, a switching member 5, and a manipulation rod 6.

The inner race 2 consists of an inner race 2A made of metal which is an example of a first metal part, and the plastic inner race 2B as described above. The metal inner race 2A has a rugged shaped portion (rugged portion) 21A at the inner periphery of a center through-hole thereof, and the rugged shaped portion 21B of the plastic inner race 2B and the rugged shaped portion 21A of the metal inner race 2A are engaged with each other such that the metal inner race 2A and the plastic inner race 2B are assembled together to prevent relative slippage in circumferential directions. Accordingly, the inner race 2 is fixed to the arm frame R1. Further, since the inner race 2 is made by assembling the metal inner race 2A and the plastic inner race 2B together, weight reduction can be achieved while ensuring the required strength.

As seen in FIG. 5, the metal inner race 2A has three roller receiving portions 26 equiangularly arranged and protruding radially outward. The outer peripheral surface of each roller receiving portion 26 is provided with a recess which is recessed toward a center of the metal inner race 2A, and the recess includes a slanted surface 22 whose radius gradually increases with distance in the clockwise direction of FIG. 5 (hereinafter, clockwise and anticlockwise directions are referred to based on the directions of FIG. 5), and an urging member receiving recess 23 which is adjacent to one end of the slanted surface 22 in the anticlockwise direction and recessed toward the center beyond the slanted surface 22. A stopper portion 24 for regulating the positional relation between an unlocking piece 41 to be described later and the metal inner race 2A is provided at an end of the slanted surface 22 in the clockwise direction. Further, a restriction wall 25 for restricting posture of a spring 72 is provided at one side of the urging member receiving recess 23 in the anticlockwise direction.

It should be noted that the rugged shaped portion 21A at the inner periphery of the metal inner race 2A has protrusive portions (portions protruding radially inward; see reference numeral 21X of FIG. 5), and the protrusive portions are arranged radially inward of the urging member receiving recesses 23. This can increase the radial width of the metal inner race 2A to avoid the presence of locally weakened portions that would occur at the metal inner race 2A.

The outer race 3 is provided radially outward of the inner race 2 (metal inner race 2A) and spaced apart from the inner race 2. The inner periphery 31 of the outer race 3 forms a circular cylindrical surface, and pockets PK each receiving a roller 71 and a spring 72 are formed between the slanted surface 22 of the metal inner race 2A and the inner periphery 31 of the outer race 3. Since the radius along the slanted surface 22 decreases with distance toward the clockwise direction while the inner periphery 31 of the outer race 3 has the circular cylindrical surface, each pocket PK includes a portion whose radial width decreases with distance toward one circumferential direction (i.e., clockwise direction).

Each unlocking piece 41 is arranged in the pocket PK adjacent to one side of the roller 71 in the one circumferential direction (i.e., clockwise direction side). The unlocking member 4 has the unlocking pieces 41. A spring 72 made of a substantially U-shaped leaf spring is arranged adjacent to the other side of the roller 71 in the one circumferential direction (i.e., anticlockwise direction side). As shown in an enlarged view in FIG. 6 (a), the spring 72 is received at its bent portion 72A in the urging member receiving recess 23 such that one arm 72B abuts on the restriction wall 25 and the other arm 72C urges the roller 71 in the clockwise direction. By this urging force the roller 71 is brought into contact with the inner walls (i.e., the slanted surface 22 and the inner periphery 31) of the pocket PK to thereby prevent backlash. It should be noted that the urging force of the spring 72 is so weak as necessary and sufficient to prevent the backlash of the roller 71, but not so strong that the roller 71 gets trapped in the inner walls of the pocket PK to lock the relative rotation between the inner race 2 and the outer race 3.

As seen in FIGS. 4 (a) and (b), the outer race 3 consists of a metal outer race 3A as an example of a second metal member and a plastic outer race 3B as an example of a second resin member.

As described above, the metal outer race 3A has an inner periphery 31 in the form of a circular cylindrical surface, and an outer periphery thereof has a rugged shaped portion (rugged portion) 32A having different outer diameters arranged at a constant pitch. The plastic outer race 3B has an inner surface provided with a rugged shaped portion 32B corresponding to the rugged shaped portion 32A, and the rugged shaped portion 32A of the metal outer race 3A and the rugged shaped portion 32B of the plastic outer race 3B are engaged with each other such that the metal outer race 3A and the plastic outer race 3B are assembled together to prevent relative slippage in circumferential directions. Accordingly, since the outer race 3 is made by assembling the metal outer race 3A and the plastic outer race 3B, weight reduction can be achieved while ensuring the required strength. When the one-way clutch 1 is in a lockable state, that is in a range from the position A to the position B during the stowing operation of the armrest R as shown in FIG. 2 (a), it is preferable that protrusive portions (portions protruding radially outward) of the rugged portion 32A formed on the outer periphery of the metal outer race 3A are arranged radially outward of the rollers 71. According to this configuration, the contact pressures of the rollers 71 can be received by high rigidity portions of the metal outer race 3A, which can ensure the strength of the metal outer race 3A.

As seen in FIG. 3, a circular support shaft 34 protrudes outward at the left-side surface of the plastic outer race 3B. Further, protrusions 39 are provided on the support shaft 34; the protrusions 39 are engageable with the seat back S1 to prevent the rotation of the outer race 3 relative to the seat back S1. Two stoppers 38 protruding radially outward (see FIG. 4 (a)) are provided on the outer periphery of the plastic outer race 3B. Further, a rotation restricting portion 35 is provided at an outer edge portion of the right-side surface of the plastic outer race 3; the rotation restricting portion 35 protrudes outward to restrict a relative rotation of the outer race 3B with respect to the switching member 5 in a predetermined angular range.

The unlocking member 4 is configured to unlock the locked state in which each roller 71 is trapped by the inner walls of the corresponding pocket PK. As seen in FIG. 3, the unlocking member 4 is made of a plate-like ring member, and has an extension portion 42 extending radially outward (e.g., lower direction in FIG. 3). The extension portion 42 is integrally molded with the main body of the unlocking member 4 and thus can be easily manufactured and the number of constituent parts can be reduced. The unlocking member 4 is configured such that the extension portion 42 is positioned between the two stoppers R4 when it is assembled with the plastic inner race 21B. To be more specific, the extension portion 42 is provided in a region where the extension portion 42 and the stoppers R4 overlap in the axial direction and where the extension portion 42 and the stoppers R4 do not overlap as viewed from the axial direction as shown in FIG. 7 (a) and FIGS. 8-10. Accordingly, the one-way clutch 1 (armrest R) can be downsized in the axial direction by effectively utilizing the space.

The extension portion 42 is provided with an engagement projection 43 with which the manipulation rod 6 is engaged. An inner peripheral portion 44 of the unlocking member 4 has a diameter corresponding to the outer diameter of the plastic inner race 2B, so that when the inner peripheral portion 44 is fitted onto the plastic inner race 2B, the unlocking member 4 is coaxial with the inner race 2 and rotatable relative to the inner race 2. Further, since the inner race 2 and the outer race 3 are rotatable relative to each other and they are not fixed to each other, the unlocking member 4 is coaxial with the inner race 2 and the outer race 3 and rotatable relative to both of the inner race 2 and the outer race 3.

The unlocking pieces 41 as described above are provided protrusively at the left-side surface of the unlocking member 4 corresponding to each of the rollers 71.

The switching member 5 is configured to cooperate with the manipulation rod 6 to switch over between the locked state and the unlocked state of the inner race 2 and the outer race 3 (rollers 71) actuated by the rotating action of the armrest R. The switching member 5 is made by a plate-like ring member, and rotatable relative to the outer race 3 because the circular inner peripheral portion 54 is engaged with the support shaft 34 of the outer race 3. Restriction walls 56, 57 protrude radially outward from the outer periphery of the switching member 5 at a position obliquely frontward and downward and at a position downward, respectively, and as seen in FIG. 7 (a), when the switching member 5 is assembled with the outer race 3, the rotation restricting portion 35 of the outer race 3 is located between the restriction wall 56 and the restriction wall 57. In other words, the switching member 5 and the outer race 3 are relatively rotatable in a range from where the rotation restricting portion 35 contacts the restriction wall 56 to where the rotation restricting portion 35 contacts the restriction wall 57. Further, since the outer race 3 and the inner race 2 are relatively rotatable, and the switching member 5 is not engaged with the inner race 2, the switching member 5 is rotatable relative to both of the inner race 2 and the outer race 3. It should be noted that while the rotation restricting portion 35 is in contact with the restriction wall 56 or the restriction wall 57, the outer race 3 and the switching member 5 can rotate together in a corresponding rotating direction.

The switching member 5 includes a small diameter portion 51 of which the outer peripheral surface extends from rear side to upper side in FIG. 3 coaxially with the inner peripheral portion 54. The small diameter portion 51 is formed with a flange extending from the peripheral edge of the switching member 5 in the axial direction (leftward). With this configuration, while the weight of the switching member 5 can be reduced, it is ensured to enlarge the sliding contact surface of the switching member 5 in contact with the contacting portion 63 of a manipulation rod 6 to be described later. Further, the switching member 5 includes a large diameter portion 52 of which the outer peripheral surface extends from rear side to the lower restriction wall 57 in FIG. 3 coaxially with the inner peripheral portion 54 and which has a diameter slightly greater than that of the small diameter portion 51. As seen in FIG. 7 (b), like the small diameter portion 51, the large diameter portion 52 is formed with a flange extending from the peripheral edge of the switching member 5 in the axial direction (leftward), so that the sliding contact surface in contact with the contacting portion 63 of the manipulation rod 6 is ensured. The flange of the small diameter portion 51 and the flange of the large diameter portion 52 are connected to each other, so that the peripheral portion of the switching member 5 has high rigidity.

Provided on the circumferential surface of the switching member 5 at the connecting portion between the small diameter portion 51 and the large diameter portion 52 is a return engagement portion 53 protruding radially outward and shaped as a small peaked projection. The return engagement portion 53 is integrally molded with the main body of the switching member 5 on the flange portions forming the small diameter portion 51 and the large diameter portion 52. With this configuration, the return engagement portion 53 can be easily manufactured and the number of constituent parts can be reduced. Further, the restriction wall 57 is adjacent to one end of the large diameter portion 52 in the clockwise direction and protrudes radially outward beyond the large diameter portion 52, so that when the contacting portion 63 slides on the large diameter portion 52, the restriction wall 57 restricts the sliding range of the contacting portion 63.

The manipulation rod 6 is configured to cooperate with the switching member 5 to manipulate locking and unlocking of the rollers 71 in accordance with the rotating action of the armrest R and the manipulation of the user. The manipulation rod 6 is made of a metal rod having rigidity to allow a slight deformation thereof, and includes a first manipulation portion 61 which is an example of a first manipulation member and extends in a circular arc shape, and a second manipulation portion 62 which is an example of a second manipulation member and extends straight along the longitudinal direction of the arm frame R1 from the front end of the first manipulation portion 61 toward the distal end of the arm frame R1. In this embodiment, the first manipulation portion 61 and the second manipulation portion 62 are integrally formed, and they do not overlap as viewed from the axial direction of the armrest R. This can reduce the size of the armrest R in the axial direction. Further, since the second manipulation portion 62 is provided along the lower edge of the arm frame R1, and the extension portion 42 of the unlocking member 4 extends downward, it is possible to prevent the armrest R from bulging upward as compared with the configuration in which the second manipulation portion 62 and the extension portion 42 are provided at the upper side of the arm frame R1.

An engagement hole 69 is formed in a connecting portion which connects the first manipulation portion 61 and the second manipulation portion 62, and the engagement hole 69 is engaged with the engagement projection 43 provided on the extension portion 42 of the unlocking member 4. The first manipulation portion 61 is arranged radially outward of the outer race 3 in a position such that the first manipulation portion 61 and the outer race 3 overlap in the axial direction (see FIG. 7 (b)). With this configuration, the size of the one-way clutch 1 does not increase in the axial direction even if the first manipulation portion 61 is provided. Accordingly, the one-way clutch can be downsized in the axial direction. The first manipulation portion 61 extends arcuately from a portion with the engagement hole 69 along the outer periphery of the outer race 3, through 90 degrees from lower side to rear side of FIG. 7 (a), and the contacting portion 63 formed by bending the first manipulation portion 61 leftward at the distal end thereof contacts the outer peripheral surface of the switching member 5 (e.g., small diameter portion 51 in the example of FIG. 7 (a)) from the radially outward side. Since the contacting portion 63 is provided by bending, the rigidity of the contacting portion 63 is enhanced. The position of the contacting portion 63 with respect to the engagement hole 69 is not limited to that in which it is separated by 90 degrees in phase about the center of rotation however, it is preferable that this position is separated away from the straight line connecting the engagement hole 69 and the center of the small diameter portion 51 and from the straight line connecting the engagement hole 69 and the center of the large diameter portion 52 as far as possible. Since the first manipulation portion 61 is engaged with the unlocking member 4, and the unlocking member 4 is relatively rotatable with respect to the outer race 3, the switching member 5 is relatively rotatable with respect to the first manipulation portion 61 in conjunction with the outer race 3.

As seen in FIG. 3, an attachment hole 65 is formed at the front end of the second manipulation portion 62. The manipulation lever R2 swingable around a shaft R3 is provided at the front end of the arm frame R1, and the front end of the second manipulation portion 62 is connected to the manipulation lever R2 at a portion thereof below the shaft R3 using the attachment hole 65 by a screw 68. Accordingly, when the lower end portion of the manipulation lever R2 is depressed rearward, the unlocking member 4 is caused to rotate in the anticlockwise direction of FIG. 7 (a) through the second manipulation portion 62.

The return engagement portion 53 protrudes from the small diameter portion 51 and the large diameter portion 52, and when the switching member 5 and the rotation restricting portion 35 are not engaged with each other (i.e., when the rotation of the switching member 5 is not restricted by the engagement between the rotation restricting portion 35 and the restriction wall 56 or by the engagement between the rotation restricting portion 35 and the restriction wall 57), the switching member 5 can be rotated by the contacting portion 63 engaged with the switching member 5. Further, the return engagement portion 53 protrudes to such an extent that when the rotation of the switching member 5 is restricted by the engagement between the rotation restricting portion 35 and the restriction wall 56 or by the engagement between the rotation restricting portion 35 and the restriction wall 57, the first manipulation portion 61 is caused to deform to allow the contacting portion 63 to ride over the return engagement portion 53.

Operation of the armrest R using the one-way clutch 1 configured as described above will be described.

With reference to FIG. 6, description will be given of the operation of the one-way mechanism implemented with the rollers 71 and the pockets PK as well as the unlocking operation implemented with the unlocking pieces 41. As seen in FIG. 6 (a), when the inner race 2 is rotated clockwise relative to the outer race 3, the space in a pocket PK rotates clockwise relative to the outer race 3, whereby a narrow portion in the pocket PK moves in a direction away from the roller 71 as far as the relation between the space in the pocket PK and the roller 71 is concerned. When attention is focused on the roller 71, the roller 71 is relatively moved toward a wider portion of a wedge-shaped space formed by the inner walls (slanted surface 22 and inner periphery 31) of the pocket PK; actually, the roller 71 does not move relatively in the pocket PK because the spring 72 urges the roller 71. Accordingly, the contact pressure between the inner walls of the pocket PK and the roller 71 does not increase, and hence the roller 71 is allowed to rotate anticlockwise in FIG. 6 (a) and the inner race 2 can be rotated relatively with respect to the outer race 3. The rotation in this direction is referred to as rotation in the unlocking direction.

On the contrary, with reference to FIG. 6 (b), when the inner race 2 is rotated anticlockwise relative to the outer race 3, the space in the pocket PK rotates anticlockwise relative to the outer race 3, whereby the narrow portion in the pocket PK moves in a direction toward the roller 71 as far as the relation between the space in the pocket PK and the roller 71 is concerned. When attention is focused on the roller 71, the roller 71 is relatively moved toward a narrower portion of the wedge-shaped space formed by the inner walls (slanted surface 22 and inner periphery 31) of the pocket PK. Accordingly, the roller 71 is trapped by the inner walls of the pocket PK and the contact pressure between the pocket PK and the roller 71 increases, which inhibits the roller 71 from rotating relative to the inner race 2 and the outer race 3. In other words, the inner race 2 and the outer race 3 are locked.

With reference to FIG. 6 (c), when an unlocking piece 41 is rotated anticlockwise relative to the inner race 2, the unlocking piece 41 comes into contact with the roller 71 to thereby urge the roller 71 anticlockwise. This can cause the roller 71 to be moved relatively toward the wider portion of the wedge-shaped space formed by the inner walls (slanted surface 22 and inner periphery 31) of the pocket PK, whereby the roller 71 is disengaged from the inner walls of the pocket PK. In this state, the inner race 2 is allowed to rotate freely both clockwise and anticlockwise relative to the outer race 3. In other words, the inner race 2 and the outer race 3 are unlocked.

As described above, when the unlocking piece 41 is not urging the roller 71 as shown in FIGS. 6 (a) and (b), the inner race 2 and the outer race 3 become non-rotatable relative to each other depending on the rotating direction of the inner race 2 and the outer race 3, and hence they are in a lockable state. In contrast, in the case shown in FIG. 6 (c), the inner race 2 can rotate relative to the outer race in any directions while slipping in the outer race 3, and hence they are in an unlocked state.

Based on the locking and unlocking principles as described above, the armrest R operates as follows.

As seen in FIG. 7 (a), when the arm frame R1 (armrest R) is located in the lowermost position, namely, when the armrest R is located in the position A in advance of the stowing operation, the rotation restricting portion 35 of the outer race 3 is located in a position between the restriction wall 56 and the restriction wall 57 and closer to the restriction wall 56, and the contacting portion 63 of the manipulation rod 6 is positioned on the small diameter portion 51 of the outer race 3 at a position closest to the large diameter portion 52 and adjacent to the return engagement portion 53. In this position, the unlocking piece 41 is not in contact with the roller 71, and as described above with reference to FIGS. 6 (a) and 6 (b), the inner race 2 and the outer race 3 are in the lockable state depending on their rotating direction. It should be noted that since the outer race 3 is fixed to the seat back S1 as described above, the outer race 3 is stationary in FIG. 7 (a) and FIGS. 8-11.

When the arm frame R1 is rotated upward from the state shown in FIG. 7 (a), the contacting portion 63 engages with a stepped portion (return engagement portion 53 in this embodiment) formed between the large diameter portion 52 and the small diameter portion 51, whereby the switching member 5 is caused to rotate clockwise relative to the outer race 3 as it is pushed by the contacting portion 63. As seen in FIG. 8, this rotation is permitted until the restriction wall 57 is brought into contact with the rotation restricting portion 35. In this rotation range (from position A to position B), the unlocking piece 41 is not in contact with the roller 71 and is in the lockable state; namely, the arm frame R1 can be rotated upward while the downward rotation thereof is inhibited. It should be noted that since the arm frame R1 rotates together with the inner race 2, the inner race 2 is rotated relatively with respect to the outer race 3 when the arm frame R1 is rotated upward.

When the arm frame R1 is rotated further upward, the rotation of the switching member 5 in the clockwise direction is inhibited as the restriction wall 57 is in contact with the rotation restricting portion 35 of the outer race 3, and as seen in FIG. 9, the contacting portion 63 rides over the return engagement portion 53 and comes into contact with the large diameter portion 52. During this time, the contacting portion 63 is pulled toward the lower right direction of FIG. 9 and the engagement hole 69 is also pulled slightly toward the lower right direction with the result that the unlocking member 4 is relatively rotated anticlockwise with respect to the inner race 2. In this instance, although the first manipulation portion 61 slightly deforms outward, the deformation amount of the first manipulation portion 61 (the moving distance of the contacting portion 63 in the radially outward direction if the engagement hole 69 is regarded as a stationary portion) is slightly smaller than the difference between the radius of the small diameter portion 51 and the radius of the large diameter portion 52, and the sum of the moving distance of the contacting portion 63 resulting from the deformation of the first manipulation portion 61 and the moving distance of the contacting portion 63 resulting from the rotation of the unlocking member 4 substantially corresponds to the difference between the radius of the small diameter portion 51 and the radius of the large diameter portion 52.

When the unlocking member 4 is relatively rotated anticlockwise with respect to the inner race 2, as described above with reference to FIG. 6 (c), each of the unlocking pieces 41 urges the roller 71 anticlockwise into the unlocked state. Namely, the inner race 2 (arm frame R1) can be rotated in any arbitrary directions relative to the outer race 3 while the contacting portion 63 is in contact with the large diameter portion 52.

When the arm frame R1 is rotated further upward, the rotation of the switching member 5 in the clockwise direction is inhibited as the restriction wall 57 is in contact with the rotation restricting portion 35 of the outer race 3, and the contacting portion 63 slides on the large diameter portion 52 while the arm frame R1 is being rotated relative to the outer race 3. As seen in FIG. 10, this rotation is permitted until the stopper R4 of the arm frame R1 is brought into contact with the stopper 38 of the outer race 3. When the stopper R4 of the arm frame R1 comes into contact with the stopper 38 of the outer race 3, the arm frame R1 has been rotated in the position C. In the range from the position of FIG. 9 to the position of FIG. 10, the arm frame R1 can be rotated arbitrarily in both upward and downward directions.

When the arm frame R1 is rotated downward during the folding out operation from the state shown in FIG. 10 toward the use position, the contacting portion 63 slides on the large diameter portion 52 in the anticlockwise direction and then engages with the return engagement portion 53 to cause the switching member 5 to rotate anticlockwise. As seen in FIG. 11, the switching member 5 rotates until the restriction wall 56 comes into contact with the rotation restricting portion 35. It should be noted that if the friction between the contacting portion 63 and the large diameter portion 52 is larger than the friction between the switching member 5 and the outer race 3, the contacting portion 63 will not slide on the large diameter portion 52, but instead the first manipulation portion 61 (contacting portion 63) and the switching member 5 together rotate anticlockwise, and the contacting portion 63 may slide on the large diameter portion 52 in the anticlockwise direction after the restriction wall 56 comes into contact with the rotation restricting portion 35; however, irrespective of the order of the motion of the contacting portion 63, the contacting portion 63 moves into the state as shown in FIG. 11. In the state shown in FIGS. 10 to 11, the contacting portion 63 is in contact with the large diameter portion 52, and the inner race 2 and the outer race 3 are in the unlocked state. Therefore, the arm rest R1 can be rotated freely in both upward and downward directions. It should be noted that FIG. 11 shows a state in which the arm frame R1 is located slightly above the position A.

When the arm frame R1 is rotated downward from the state shown in FIG. 11, the rotation of the switching member 5 in the anticlockwise direction is inhibited as the restriction wall 56 is in contact with the rotation restricting portion 35, and the contacting portion 63 rides over the return engagement portion 53 while the first manipulation portion 61 is being deformed and then comes into contact with the small diameter portion 51. The contacting portion 63 then returns to the state shown in FIG. 7 (a). During this time, that position which the contacting portion 63 contacts the outer peripheral surface of the switching member 5 is switched from the large diameter portion 52 to the small diameter portion 51, and in contrast to the change from the state shown in FIG. 8 to the state shown in FIG. 9, the unlocking member 4 slightly rotates clockwise relative to the inner race 2. This can cause each of the unlocking pieces 41 not to urge the roller 71, and as described above with reference to FIGS. 6 (a) and (b), the inner race 2 and the outer race 3 return to the lockable state.

As described above, according to the one-way clutch 1 in this embodiment, the locked state and the unlocked state can be switched over by the predetermined rotating action of the armrest R (arm frame R1). Further, since the one-way clutch 1 is not of the type using a coil spring wound around a shaft as in the case of the conventional armrest, and is configured to use rollers 71 received in wedge-shaped pockets PK, the size of the one-way clutch 1 can be reduced in the axial direction.

Further, as describe above, since the switching member 5 is rotatable relative to both of the inner race 2 and the outer race 3, and the rotation range thereof is restricted by the rotation restricting portion 35 and the restriction walls 56, 57, and further the return engagement portion 53 is provided on the switching member 5, the arm frame R1 can be moved from up to down and from down to tip.

Further, in addition to the above motions, depressing the lower end portion of the manipulation lever R2 causes the unlocking member 4 to rotate anticlockwise through the second manipulation portion 62. This can allow the user to unlock at any time irrespective of the orientation of the arm frame R1 and/or the position of the contacting portion 63 in contact with the switching member 5. In other words, the easy operability can be improved.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment and various changes and modifications may be made where necessary.

For example, as seen in FIG. 12, al inner wall of a pocket PK may be provided with a projection 22A at one side of the roller 71 in a direction where the radial width of the pocket PK decreases and adjacent to the roller 71. With this configuration, when the inner race 2 and the outer race 3 are forcibly and relatively rotated in the locking direction, the projection 22A and the roller 71 are brought into contact so that the contact pressure between the roller 71 and the inner walls of the pocket PK does not increase any further. This can prevent the inner race 2 and the outer race 3 from receiving an excessive radial load. It should be noted that the projection may be provided on the inner periphery 31 of the outer race 3.

Further, three roller receiving portions 26 are provided in the above embodiment; however, the number of the roller receiving portions 26 is not limited as long as one or more roller receiving portion are provided. For smooth rotation of the inner race 2 and the outer race 3, the more roller receiving portions 26, at least three or more, are preferable.

In the above embodiment, the inner race 2 is fixed to the arm frame R1 and the outer race 3 is fixed to the seat back S1; however, the outer race 3 may be fixed to the arm frame R1 and the inner race 2 may be fixed to the seat back S1 instead. In this instance, it is to be understood, of course, that the orientation of the wedge-shaped pocket PK may be changed where appropriate.

Locking and unlocking the inner race 2 and the outer race 3 in accordance with the rotation of the unlocking member 4 in either of the circumferential directions can be modified where necessary in consideration of the orientation of the wedge-shaped pockets PK.

In the above embodiment, rollers 71 are exemplified as an example of movable pieces: however, the movable pieces may be balls. As long as the sliding property is properly set, block-shaped or wedge-shaped small pieces each of which does not roll over relative to the inner race 2 and the outer race 3 may be used.

The first manipulation member may not be engaged with the unlocking member but may be fixed thereto. Even in this configuration, if the rigidity of the first manipulation member is set to allow the contacting portion of the first manipulation member to deform to ride over from the small diameter portion to the large diameter portion, the switching between locking and unlocking can be made by the rotation of the unlocking member. Similarly, the second manipulation portion may be fixed to the unlocking member.

In the above embodiment, the inner periphery of the outer race 3 forms a circular cylindrical surface and recesses are formed in the outer periphery (roller receiving portions 26) of the inner race 2 to provide pockets PK; however, the outer periphery of the inner race 2 may form a circular cylindrical surface and recesses may be formed in the outer race 3 to provide pockets PK.

In the above embodiment, the rotation restricting portion 35 is provided on the outer race 3; however, the rotation restricting portion 35 may be provided on the inner race 2.

In the above embodiment, the unlocked state is achieved when the contacting portion 63 is in contact with the large diameter portion 52, whereas the lockable state is achieved when the contacting portion is in contact with the small diameter portion 51; however, using the same principle of switching the locked state and the lockable state by the rotation of the unlocking member 4, the lockable state may be achieved when the contacting portion 63 is in contact with the large diameter portion 52, whereas the unlocked state may be achieved when the contacting portion is in contact with the small diameter portion 51. Further, the circumferential surface of the unlocking member 4 to which the contacting portion 63 contacts may be the inner peripheral surface instead of the outer peripheral surface. In this instance, the return engagement portion 53 protrudes inward.

In the above embodiment, the switching member 5 is configured to be rotatable in conjunction with the outer race 3; however, the switching member 5 may be rotatable in conjunction with the inner race 2.

In the above embodiment, the return engagement portion 53 is provided at the connecting portion between the small diameter portion 51 and the large diameter portion 52; however, the return engagement portion 53 may be provided on the large diameter portion 52 or on the small diameter portion 51.

In the above embodiment, the spring 72 is exemplified as an example of the urging member; however, the urging member may be a rubber damper.

In the above embodiment, the one-way clutch 1 is exemplified as an example of the clutch; however, the clutch may be a two-way clutch which is engageable (lockable) when the inner race and the outer race rotate in any directions. For example, a movable piece (roller 71), a pocket PK, an unlocking piece 41 and the like may be provided symmetrically with respect to the spring 72.

In the above embodiment, the one-way clutch is exemplified to support the armrest. However, the use of the one-way clutch is not limited to this specific configuration. For example, the one-way clutch according to the present invention is applicable to a movable lumbar support, a height adjustment mechanism of a seat, a tilt-angle adjustable headrest which is rotatable in forward and rearward directions, and a movable ottoman (footrest). Further, in the above embodiment, the switching member 5 is configured to be rotatable relative to the outer race 3; however, the switching member may be configured not to be relatively rotatable (e.g., rotatable together) with respect to the outer race. In this instance, the return engagement portion 53 is not provided (may be provided though it is not necessary) anywhere on the whole outer peripheral surface (whole range of 360 degrees) of the switching member, part of which may be formed as the large diameter portion 52 and the rest of which may be formed as the small diameter portion. With this configuration, a rotating member corresponding to the arm frame R1 can rotate freely in a range where the contacting portion 63 is in contact with the large diameter portion 52, and rotate only in one direction in a range where the contacting portion 63 is in contact with the small diameter portion 51. 

1. An armrest attachable to a seat back, comprising: an arm frame; and a clutch through which the arm frame is rotatably supported by the seat back, wherein the clutch comprises: an inner member configured to be fixed to one of the arm frame and the seat back; an outer race provided radially outward of the inner member and spaced apart from the inner member, and configured to be fixed to the other one of the arm frame and the seat back; an unlocking member provided coaxially with the inner member and the outer race, and configured to be rotatable relative to both of the inner member and the outer race; and an unlocking manipulation mechanism configured to actuate the unlocking member to unlock a locked state.
 2. The armrest according to claim 1, wherein the inner member is an inner race, wherein the armrest comprises a movable piece received in a pocket which is located between the inner race and the outer race and includes a portion whose radial width decreases with distance toward one circumferential direction, wherein the unlocking member has an unlocking piece arranged adjacent to one side of the movable piece in the one circumferential direction, and wherein the unlocking manipulation mechanism is configured to actuate the unlocking member to unlock the locked state in which the movable piece is trapped by inner walls of the pocket.
 3. The armrest according to claim 2, wherein the clutch is a one-way clutch, and the unlocking manipulation mechanism includes a first manipulation member configured to be engaged with or fixed to the unlocking member, and a switching member configured to be coaxial with and rotatable relative to both of the inner race and the outer race and having a circumferential surface, wherein the first manipulation member contacts the circumferential surface of the switching member, and the circumferential surface of the switching member includes a small diameter portion and a large diameter portion having a diameter greater than that of the small diameter portion, wherein one of the inner race and the outer race has a rotation restricting portion engageable with the switching member to restrict a relative rotation thereof with respect to the switching member in a predetermined angular range, wherein the circumferential surface is provided with a return engagement portion protruding radially from the circumferential surface, and wherein when the first manipulation member is brought into contact with one of the small diameter portion and the large diameter portion, the unlocking member is allowed to rotate in the one circumferential direction to cause the movable piece to be trapped and thus locked by the inner walls of the pocket, whereas when the first manipulation member is brought into contact with the other one of the small diameter portion and the large diameter portion, the unlocking member is allowed to rotate in the other circumferential direction to unlock the locked state of the movable piece.
 4. The armrest according to claim 2, wherein the inner race comprises a first metal part constituting a part of the inner walls of the pocket, and a first resin part, and wherein a rugged portion formed on an inner periphery of the first metal part and a rugged portion formed on an outer periphery of the first resin part are engaged with each other such that the first metal part and the first resin part are assembled together to prevent relative slippage in circumferential directions.
 5. The armrest according to claim 2, further comprising an urging member arranged to urge the movable piece toward the one circumferential direction, wherein the inner race comprises a first metal part constituting a part of the inner walls of the pocket, and a first resin part, wherein a rugged portion formed on an inner periphery of the first metal part and a rugged portion formed on an outer periphery of the first resin part are engaged with each other such that the first metal part and the first resin part are assembled together to prevent relative slippage in circumferential directions, wherein at the outer periphery of the first metal part, the first metal part has an urging member receiving recess which is recessed toward a center of the first metal part to receive the urging member, and wherein the rugged portion of the first metal part has a protrusive portion protruding toward the center of the first metal part, and the protrusive portion is arranged radially inward of the urging member receiving recess.
 6. The armrest according to claim 2, wherein the outer race comprises a second metal part constituting a part of the inner walls of the pocket, and a second resin part, and wherein a rugged portion formed on an outer periphery of the second metal part and a rugged portion formed on an inner periphery of the second resin part are engaged with each other such that the second metal part and the second resin part are assembled together to prevent relative slippage in circumferential directions.
 7. The armrest according to claim 6, wherein the rugged portion of the second metal part has a protrusive portion protruding radially outward, and when the clutch is in the locked state, the protrusive portion is positioned radially outward of the movable piece.
 8. The armrest according to claim 2, wherein the unlocking member has an extension portion extending radially outward, and wherein the first manipulation member engages with the unlocking member at the extension portion, and the first manipulation member is arranged radially outward of the outer race in a region where the first manipulation member and the outer race overlap in an axial direction.
 9. The armrest according to claim 2, wherein the inner walls of the pocket have a projection at one side of the movable piece in the one circumferential direction, and when the inner race and the outer race are forcibly and relatively rotated in a locking direction, the projection contacts the movable piece.
 10. The armrest according to claim 2, wherein the unlocking manipulation mechanism is engaged with or fixed to the unlocking member and includes a second manipulation member extending toward a distal end of the arm frame, and wherein when the second manipulation member is manipulated to rotate the unlocking member in the other circumferential direction, the movable piece is allowed to be unlocked.
 11. The armrest according to claim 3, wherein the unlocking manipulation mechanism is engaged with or fixed to the unlocking member and includes a second manipulation member extending toward a distal end of the arm frame, wherein when the second manipulation member is manipulated to rotate the unlocking member in the other circumferential direction, the movable piece is allowed to be unlocked, wherein the first manipulation member is provided arcuately around an axis of rotation of the arm frame, and the second manipulation member is provided along a longitudinal direction of the arm frame, and wherein the first manipulation member and the second manipulation member are arranged so as not to overlap each other as viewed from an axial direction.
 12. The armrest according to claim 3, wherein the small diameter portion and the large diameter portion are formed as flanges extending from a peripheral edge of the switching member in an axial direction of the switching member.
 13. The armrest according to claim 12, wherein the flange constituting the small diameter portion and the flange constituting the large diameter portion are connected to each other.
 14. The armrest according to claim 3, wherein the return engagement portion is integrally molded with the switching member.
 15. The armrest according to claim 8, wherein the extension portion is integrally molded with the unlocking member.
 16. The armrest according to claim 8, wherein a first attachment member is fixed to the inner race and a second attachment member is fixed to the outer race, wherein one of the first attachment member and the second attachment member has a stopper which protrudes toward the one-way clutch and is engageable with the inner race or the outer race fixed to the other one of the first attachment member and the second attachment member to restrict a rotation range of the one of the first attachment member and the second attachment member, and wherein the stopper is arranged in a region where the stopper and the extension portion overlap in the axial direction and where the stopper and the extension portion do not overlap as viewed from the axial direction. 